Two-Stage Aquaprocessing Before Steam Cracking to Limit Coking
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Solution Overview
Problem
The high cost and coking issues in conventional hydrocrackers used for converting crude oil streams to produce olefins and aromatics, along with the high investment required in steam crackers and hydrocrackers, lead to inefficiencies and reduced uptime due to coke buildup.
Innovation Solution
A two-stage aquaprocessing method is employed, utilizing fixed bed hydroprocessing units for the majority of the flow and ebullated/slurry reactors for a sub-stream, followed by steam cracking to produce olefins and aromatics, allowing for efficient conversion and minimizing coke-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fixed bed hydrocrackers are used for conversion of crude oil fractions, then investment cost is reduced, but coke buildup occurs leading to reduced time on stream
Solution Approach 1:
The crude oil feed is divided into multiple fractions (vacuum gas oil, atmospheric residue, etc.) that are processed separately through different reactor types. This segmentation allows each fraction to be optimized for its specific properties, preventing coke buildup in fixed bed reactors while maintaining cost effectiveness.
Solution Approach 2:
Different reactor types are assigned to different feed streams based on their specific characteristics. Fixed bed hydrocrackers handle lighter vacuum gas oil fractions, while slurry/ebullated bed reactors handle heavier atmospheric residue fractions more prone to coking. This local optimization resolves the contradiction between cost and reliability.
2Reliability
If slurry and ebullated bed reactors are used to handle coke, then time on stream is improved, but device cost increases
Solution Approach 1:
The feed stream is segmented by boiling point range and feedstock type, directing only the heavy atmospheric residue fraction to expensive slurry/ebullated bed reactors capable of handling coke, while lighter fractions are processed in cheaper fixed bed reactors. This selective application minimizes overall device cost while maintaining reliability where needed.
Solution Approach 2:
The solution applies different reactor technologies to different locations in the process flow based on local feedstock requirements. The expensive coke-tolerant reactors are deployed only where necessary (atmospheric residue stream), while standard fixed bed reactors handle the majority of lighter fractions, optimizing the balance between reliability and cost.
3Productivity
If high conversion of crude oil streams is achieved, then productivity is improved, but coke buildup increases leading to reduced time on stream
Solution Approach 1:
The conversion process is segmented into multiple stages with different severity levels. Mild hydrocracking in fixed bed reactors provides initial conversion, followed by more severe hydrocracking in slurry/ebullated bed reactors for the heavy fraction. This staged approach achieves high overall conversion while distributing coke formation across different reactor types, maintaining time on stream.
Solution Approach 2:
The process utilizes parameter changes by operating different reactor types at different temperatures, pressures, and LHSV values optimized for their specific feedstocks and conversion requirements. This allows high overall conversion efficiency while each reactor operates within parameters that minimize its specific drawbacks.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces costs by utilizing less expensive fixed bed reactors while maximizing conversion efficiency and avoiding pressure drop issues, thereby enhancing the production of high-value chemicals like olefins and aromatics.
Implementation Method 1
Aquaprocessing is the hydrocracking of hydrocarbons in the presence of (a) one or more catalysts and (b) a solvent to keep asphaltenes dissolved, at a temperature in the range of 280 to 550° C. and a pressure in the range of 40 to 200 barg
Implementation Method 2
Aquaprocessing is the hydrocracking of hydrocarbons in the presence of (a) one or more catalysts and (b) a solvent to keep asphaltenes dissolved
Implementation Method 3
processing the second top stream in a steam cracking unit to produce olefins and/or aromatics
Data Source
AI summary
Systems and methods for producing olefins and/or aromatics are disclosed. The methods include using two stages of aquaprocessing of crude and/or heavy oils prior and subsequent processing in a steam cracking unit to produce olefins and/or aromatics. A first aquaprocessing stage and a second aquaprocessing stage are operated at different severities. The systems include two aquaprocessing units capable of being operated at different severities.